Regrettably, you can only post one question at a time. From the ones offered, I chose to explore the question regarding the Jewish prayer for the dead. I think that Wiesel's own words would be helpful here:

Someone began to recite the Khaddish, the prayer for the dead. I do not know if it has ever happened before, in the long history of the Jews, that people have ever recited the prayer for the dead for themselves.

The Khaddish is the Jewish prayer for the dead. It is used for purposes of mourning in the Jewish faith. Wiesel includes the Khaddish for a couple of reasons. On one hand, people like Akiba Drumer cling to the Khaddish as part of their faith. Yet, over the course of the narrative, the horrors of the Holocaust compel individuals to recite it even when those are alive, as reflective of the pure terror that is being endured. At the same time, the desire to recite the Khaddish is something that is forgotten, such as in Akiba Drumer's case. This omission reflects how faith was trampled during the Holocaust. The presence of death was something so pervasive and so expansive that the purpose of mourning it, the primary purpose of the Khaddish, was lost in the Holocaust. It becomes difficult to mourn that which is the norm and replacing the spirit of life and living.